Publications

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    ABSTRACT: The purpose of the study was to compare the seasonal changes (preparation period: PP and competition period: CP) of vertical jumping performance and knee muscle strength in a team of under-19 women volleyball players (N=12, 16.2 ± 1.5 yrs). The countermovement jump was used to evaluate jumping performance. The isometric knee extension moment at 150 ms from the onset of contraction (T150) and at a maximum of contraction (TMAX) were determined at nine knee angles (from 10° to 90°, full knee extension = 0°). The peak isokinetic knee extension (TISOK-EXT) and flexion (TISOK-FLEX) moment were determined at 60, 180 and 240°·s. Repeated measures analysis of variance was applied to the differences between PP and CP (p ≤ 0.05). Significant increases in jumping performance were found for jump height, peak impulse, total impulse, peak power and take-off velocity (p ≤ 0.05). T150 was significantly increased (p ≤ 0.05) at the knee flexion angles from 40° to 90°, whereas the increase was not significant at the rather extended knee angles of 10°, 20° and 30° (p > 0.05). TMAX was significantly increased only at 90° of knee flexion (p ≤ 0.05). With the exception of TISOK-FLEX at 60°·s (p ≤ 0.05), the increases of TISOK-EXT and TISOK-FLEX were not significant (p > 0.05). The TISOK-EXT / TISOK-FLEX ratios were not significantly changed (p > 0.05). The main application of the study is that it provides performance standards and potential criteria for variable selection for jumping performance and knee muscle strength seasonal evaluation.
    The Journal of Strength and Conditioning Research 06/2012; · 1.80 Impact Factor
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    ABSTRACT: The purpose of this study was to determine the effects of a specific warm-up using half-squats at low and moderate intensity on vertical jump performance and electromyographic activity of the thigh muscles. The subjects were 26 men who were divided into a low intensity group (LIG; n = 13) and a moderate intensity group (MIG; n = 13). The LIG performed a specific warm-up protocol that included the explosive execution of half-squats with loads 25 and 35% of the one repetition maximum (1RM) and the MIG with loads 45 and 65% of the 1RM. The two groups performed a countermovement jump (CMJ) before and three minutes after the specific warm-up protocols. During the concentric phase of the CMJ a linear encoder connected to an A/D converter interfaced to a PC with a software for data acquisition and analysis allowed the calculation of average mechanical power. The electromyographic (EMG) activity of the vastus lateralis (VL), vastus medialis (VM) and rectus femoris (RF) were recorded during the concentric phase of the jumps. The average quadriceps (Qc) activity (mean value of the VL, VM and RF) was also calculated. A two way ANOVA (protocols X time) with repeated measures on the second factor was used to analyze the data. Following the specific warm-up procedure both groups improved (p ≤ 0.05) CMJ performance and mechanical power by 3.5% and 6.3%, respectively, with no differences observed between the two groups. EMG activity of the Qc and VL increased (p ≤ 0.05) for both groups by 5.9% and 8.5%, respectively. It is concluded that the use of a specific warm-up that includes half-squats, performed explosively with low to moderate intensity, improves CMJ performance. This may be due to increased muscle activation as evaluated by the surface EMG. Key pointsThe inclusion of two sets of explosively performed half squats with low to moderate loads in the warm up procedure elicited an acute performance en-hancement.The performance was enhanced regardless of the load used in the warm-up.The performance enhancement is accompanied by a greater electromyographic activity of the knee extensors muscles.
    Journal of sports science & medicine 01/2010; 9(2):326-31. · 0.89 Impact Factor
  • Barzouka Karolina, Malousaris Grigorios
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    ABSTRACT: In physical education there is a two-way relation between acquiring moving skills and the mechanisms ofimpulsion. The goal of the present text was to confirm the effect of this kind of model observation on theinternal impulsion of the participants. Fifty three high school girls of 12-15 years old, separated randomly intolevels, in three teams and practiced in one common intervention programme consisted of 12 practice sessions forthe volleyball skill acquisition (the serve skill – ball reception). The participants of the 1st and the 2ndexperimental teams were receiving as feedback a model observation, while all the three teams were receivingverbal instructions during the intervention programme. At the beginning and the end of the intervention the trainees fulfilled the questionary (Ryan 1982) for the internal impulsion. For the statistic process of the internal impulsion data, the method of fluctuation analysis with 2 factors (3X2) was used. The level of importance wasdefined as p<0.5. The outcome demonstrated that no type of feedback influenced essentially the internal impulsion. There were only tendencies in favor of the second group.
    Citius Altius Fortius. 01/2009;
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    ABSTRACT: The purpose of this study was the examination and comparison of performance in attack in relationship with performance in set between Olympic-level volleyball male (M) and female (F) players. A 3-member group of expert coaches assessed the players' actions in set and attack in 16 volleyball games (M=8, F=8) of teams competing in the final phase of the 2004 Olympic Games. Assessment was based on a 5-point rating scale (Eom and Schutz, 1992) and included actions that composed a set of 2 contacts in Complex I (M=1007, F=1248). A cross tabulation statistical procedure with level 4 x 5 calculated performance percentages and frequencies; X 2 criterion was used to examine possible differences in the distribution of performance assessment in attack for every performance assessment in set and Z criterion was used to compare percentages of performance assessment between genders. Results showed that the higher the performance of setters, the higher the performance of attackers in both genders. Significantly (P<0.05) lower percentages of male compared to female attackers' average and very good performance were found after receiving good and excellent quality sets, whereas significantly (P<0.05) higher percentages of good performance were shown in favor of male attackers after receiving excellent quality sets.
    International Journal of Performance Analysis of Sport. 01/2009; 9:141-148.
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    ABSTRACT: The aim of this study was to describe the morphological characteristics of competitive female volleyball players. For this purpose, body weight and height, breadths and girths as well as skinfold thickness at various body sites were assessed in 163 elite female volleyball players (age: 23.8+/-4.7 years, years of playing: 11.5+/-4.2, hours of training per week: 11.9+/-2.9, means+/-S.D.). Seventy-nine of these players were from the A1 division and the rest from the A2 division of the Greek National League. Two-way ANOVA was used to compare the differences in these characteristics between competition level and playing position. Body height ranged from 161cm to 194cm, and the mean value (177.1+/-6.5cm) was not inferior to that of international players of similar calibre. Adiposity of these players (sum of 5 skinfolds: 51.8+/-10.2mm, percent body fat: 23.4+/-2.8) was higher than that reported in other studies in which, however, different methodology was used. Volleyball athletes of this study were mainly balanced endomorphs (3.4-2.7-2.9). The A1 division players were taller and slightly leaner with greater fat-free mass than their A2 counterparts. Significant differences were found among athletes of different playing positions which are interpreted by their varying roles and physical demands during a volleyball game. The volleyball players who play as opposites were the only subgroup of players differing between divisions; the A2 opposites had more body fat than A1 opposites. These data could be added in the international literature related to the anthropometric characteristics of competitive female volleyball players.
    Journal of Science and Medicine in Sport 07/2008; 11(3):337-44. · 2.90 Impact Factor
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    ABSTRACT: This study examined the effect of feedback with simultaneous skilled model observation and self-modeling on volleyball skill acquisition. 53 pupils 12 to 15 years old formed two experimental groups and one control group who followed an intervention program with 12 practice sessions for acquisition and retention of how to receive a ball. Groups received different types of feedback before and in the middle of each practice session. Reception performance outcome (score) and technique in every group were assessed before and at the end of the intervention program and during the retention phase. A 3 (Group) x 3 (Measurement Period) multivariate analysis of variance with repeated measures was applied to investigate differences. Results showed equivalent improvement in all three groups at the end of the intervention program. In conclusion, types of augmented feedback from the physical education teacher are effective in acquisition and retention of the skill for reception in volleyball.
    Perceptual and Motor Skills 03/2007; 104(1):32-42. · 0.49 Impact Factor
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    ABSTRACT: Feedback that is being provided in the form of instructional cues and model observation has systematically been used for skill acquisition. The purpose of this study was to examine the effect of feedback provided with instructional cues together with simultaneous model observation and self modeling on volleyball skill acquisition. Fifty three high-school female pupils aged 12 to 15 were randomly assigned into 3 groups and received a common intervention program of 12 practice sessions for the learning of Service. Feedback for participants in the 1st and 2nd group was provided with different type of model demonstration, whereas all groups received verbal instructions. The outcome and technique in Service were evaluated before and after the completion of the intervention program, as well as during the retention phase. Results showed equivalent improvement only in technique (p<.01) but not in outcome. In conclusion, it appears that every type of augmented feedback provided with instructional cues and model observation is effective for motor skill acquisition.
    Inquiries in Sport & Physical Education. 01/2006;

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